Haven't shot an E-520, but I think if you're upgrading from a SeaLife you have a LOT of room to grow. I wouldn't necessarily just consider the Oly housing, though, as there are other housings out there that might also give you some flexibility. The Oly housing as I understand it has 5 ports, which I think alone would give you LOTS of room to grow and improve your skill set, but the thing I find most limiting is the strobe bulkhead, which appears to be limited to the Olympus UFL strobe. The Ikelite housing on the other hand gives you a bit more flexibility there, with special sync cords that will allow you to use your YS-110... Possibly not in true TTL mode, but you may need to talk to the Ike experts on that. For me, I mostly shoot manual anyway, and fortunately the YS-110 gives you plenty of settings to do that with.